"tallg said So if it works out cheaper ...

So if it works out cheaper to fly London -> Doha -> Dubai it makes sense to book a nights lay-over in Doha and then just not get the connecting flight to Dubai, and vice-versa on the return leg."

It may work fine for the London>Doha, but if you do not show up in Dubai for the return flight, they would have no obligation to keep your seat for the Doha>London part.